Method and apparatus for beamforming

ABSTRACT

Embodiments of a method and an apparatus for beamforming are disclosed. In an embodiment, a method for beamforming involves transmitting, by a beamformer to a beamformee, a sounding packet that includes training symbols, receiving, at the beamformee, the sounding packet that includes the training symbols, deriving, at the beamformee, channel estimates from the training symbols included in the sounding packet, computing, at the beamformee, a feedback matrix from the derived channel estimates, transmitting, by the beamformee to the beamformer, a packet that includes two sets of symbols, where the feedback matrix is applied to at least one of the two sets of symbols, receiving, at the beamformer, the packet that includes the two sets of symbols, and operating the beamformer according to the two sets of symbols included in the packet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of India Provisional PatentApplication Serial Number 202021030011, filed on Jul. 14, 2020, which isincorporated by reference herein.

BACKGROUND

In beamforming systems, beamforming devices, e.g., beamformers orbeamformees, can exchange wireless information and execute variouswireless operations in response to the wireless information. As anexample, symbols may be transmitted via packets by a beamformer to abeamformee to help direct beam steering in subsequent packettransmissions. In such an example, an implicit beamforming technique oran explicit beamforming technique may be used to support beamformingbetween the beamformer and the beamformee. However, because the implicitbeamforming technique and/or the explicit beamforming technique may notbe able to easily support devices with large number of antennas (e.g.,16 antennas), beamforming systems may experience limited performance andrange capabilities.

SUMMARY

Embodiments of a method and an apparatus for beamforming are disclosed.In an embodiment, a method for beamforming involves transmitting, by abeamformer to a beamformee, a sounding packet that includes trainingsymbols, receiving, at the beamformee, the sounding packet that includesthe training symbols, deriving, at the beamformee, channel estimatesfrom the training symbols included in the sounding packet, computing, atthe beamformee, a feedback matrix from the derived channel estimates,transmitting, by the beamformee to the beamformer, a packet thatincludes two sets of symbols, where the feedback matrix is applied to atleast one of the two sets of symbols, receiving, at the beamformer, thepacket that includes the two sets of symbols, and operating thebeamformer according to the two sets of symbols included in the packet.

In an embodiment, the sounding packet includes at least as many trainingsymbols as a number of antennas at the beamformer (N_(Tx)).

In an embodiment, the feedback matrix includes right singular vectorsderived from the channel estimates.

In an embodiment, the beamformer directs beam steering to the beamformeeusing the right singular vectors derived from the channel estimates.

In an embodiment, the packet that includes the two sets of symbolsincludes a first set of symbols that include a sequence of trainingsymbols, and a second set of symbols that include the sequence oftraining symbols included in the first set of symbols with the appliedfeedback matrix.

In an embodiment, columns of the applied feedback matrix are anorthonormal spatial spreading matrix, and where the beamformee appliesanother orthonormal matrix to the first set of symbols and applies thefeedback matrix in addition to the orthonormal matrix to the second setof symbols.

In an embodiment, the first set of symbols includes at least as manytraining symbols as a number of spatial streams (N_(SS)) and the secondset of symbols includes at least as many training symbols as N_(Tx).

In an embodiment, columns of the applied feedback matrix are anorthonormal spatial spreading matrix.

In an embodiment, the packet that includes the two sets of symbolsincludes a first set of symbols that include a sequence of trainingsymbols, and a second set of symbols that include the sequence oftraining symbols included in the first set of symbols with the appliedorthonormal spatial spreading matrix.

In an embodiment, the beamformee applies another orthonormal matrix tothe first set of symbols and applies the feedback matrix in addition tothe orthonormal matrix to the second set of symbols.

In an embodiment, the first set of symbols includes at least as manytraining symbols as N_(SS) and the second set of symbols includes atleast as many training symbols as N_(Tx).

In an embodiment, the beamformer computes two sets of channelcoefficients from the packet that includes the two sets of symbols.

In an embodiment, the beamformer recovers the feedback matrix using thetwo sets of channel coefficients.

In an embodiment, recovering the feedback matrix using the two sets ofchannel coefficients includes computing a first orthonormal matrix by:deriving a first Hermitian transpose of a first channel coefficientmatrix from at least one of the two sets of channel coefficients,deriving a first QR decomposition of the first Hermitian transpose todetermine the first orthonormal matrix, computing a second orthonormalmatrix by: deriving a second Hermitian transpose of a second channelcoefficient matrix from at least one of the two sets of channelcoefficients, deriving a second QR decomposition of the second Hermitiantranspose to determine the second orthonormal matrix, and deriving athird matrix with orthogonal columns from the first orthonormal matrixand the second orthonormal matrix, where the third matrix is thefeedback matrix.

In an embodiment, the beamformer selects corresponding columns from thesecond orthonormal matrix and post-multiplies a sub-matrix formed by thecorresponding columns from the second orthonormal matrix with the firstHermitian transpose of the first orthonormal matrix to derive the thirdmatrix with orthogonal columns.

In an embodiment, the training symbols included in the packet are LongTraining Field (LTF) symbols.

In an embodiment, the first set of symbols is repeated N times and thesecond set of symbols is repeated M times, where N and M are integersgreater than one.

In an embodiment, the beamformee transmits at least one data symbol thatincludes at least one sub-stream signal-to-noise ratio (SNR).

An embodiment of a beamforming system is also disclosed. The beamformingsystem includes a beamformer including a processor configured to:transmit a sounding packet that includes training symbols, receive apacket that includes two sets of symbols, operate according to the twosets of symbols included in the packet, a beamformee including aprocessor configured to: receive the sounding packet that includes thetraining symbols, derive channel estimates from the training symbolsincluded in the sounding packet, compute a feedback matrix from thederived channel estimates, and transmit the packet that includes the twosets of symbols, where the feedback matrix is applied to at least one ofthe two sets of symbols.

An embodiment of a device is also disclosed. The device includes aprocessor configured to operate as a beamformer, where operating as abeamformer involves: transmitting a sounding packet that includestraining symbols, receiving a packet that includes two sets of symbols,operating according to the two sets of symbols included in the packet,and operate as a beamformee, where operating as a beamformee involves:receiving the sounding packet that includes the training symbols,deriving channel estimates from the training symbols included in thesounding packet, computing a feedback matrix from the derived channelestimates, and transmitting the packet that includes the two sets ofsymbols, where the feedback matrix is applied to at least one of the twosets of symbols.

Other aspects in accordance with the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrated by way of example of the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a beamforming system.

FIG. 2 illustrates an example of a beamformer and a beamformeeexchanging packets in accordance with an embodiment of the invention.

FIG. 3 depicts an example of a packet in accordance with an embodimentof the invention.

FIG. 4A depicts another example of a packet in accordance with anembodiment of the invention.

FIG. 4B depicts another example of a packet in accordance with anembodiment of the invention.

FIG. 5 depicts a functional block diagram of operations at a beamformerand a beamformee while exchanging packets in accordance with anembodiment of the invention.

FIG. 6 illustrates an example of operations between a beamformer and abeamformee while exchanging packets to direct beam steering inaccordance with an embodiment of the invention.

FIG. 7 illustrates a flow diagram of a technique for beamforming inaccordance with an embodiment of the invention.

Throughout the description, similar reference numbers may be used toidentify similar elements.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments asgenerally described herein and illustrated in the appended figures couldbe arranged and designed in a wide variety of different configurations.Thus, the following more detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thepresent disclosure, but is merely representative of various embodiments.While the various aspects of the embodiments are presented in drawings,the drawings are not necessarily drawn to scale unless specificallyindicated.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by this detailed description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present invention should be or are in anysingle embodiment of the invention. Rather, language referring to thefeatures and advantages is understood to mean that a specific feature,advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present invention. Thus,discussions of the features and advantages, and similar language,throughout this specification may, but do not necessarily, refer to thesame embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the invention can be practiced without oneor more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments of the invention.

Reference throughout this specification to “one embodiment”, “anembodiment”, or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment of the presentinvention. Thus, the phrases “in one embodiment”, “in an embodiment”,and similar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

In embodiments of a beamforming system (e.g., a wireless communicationssystem), a device, e.g., a beamformer (e.g., an access point (AP)multi-link device (MLD) of a wireless local area network (WLAN)) maytransmit data to at least one associated beamformee (e.g., a station(STA) MLD). The beamformer may be configured to operate with associatedbeamformees according to a communication protocol. For example, thecommunication protocol may be an Extremely High Throughput (EHT)communication protocol, or Institute of Electrical and ElectronicsEngineers (IEEE) 802.11be communication protocol.

Features of beamforming and wireless communication systems operating inaccordance with the EHT communication protocol and/or next-generationcommunication protocols may be referred to herein as “non-legacy”features. In some embodiments of the beamforming system describedherein, different associated beamformees within range of a beamformeroperating according to the EHT communication protocol may be configuredto operate according to at least one other communication protocol, butmay be affiliated with lower data throughput protocols. The lower datathroughput communication protocols (e.g., High Efficiency (HE)communication protocol, Very High Throughput (VHT) communicationprotocol, etc.) may be collectively referred to herein as “legacy”communication protocols.

FIG. 1 depicts a beamforming system 100 that is used for wireless (e.g.,WiFi) communications. In the embodiment depicted in FIG. 1, thebeamforming system includes one beamformer device, which is implementedas beamformer 104, and one beamformee device, which is implemented asbeamformee 108. The beamforming system can be used in variousapplications, such as industrial applications, medical applications,computer applications, and/or consumer or enterprise applications. Insome embodiments, the beamforming system is a wireless communicationssystem, such as a wireless communications system compatible with an IEEE802.11 protocol. For example, the beamforming system may be a wirelesscommunications system compatible with the IEEE 802.11be protocol.Although the depicted beamforming system 100 is shown in FIG. 1 withcertain components and described with certain functionality herein,other embodiments of the beamforming system may include fewer or morecomponents to implement the same, less, or more functionality. Forexample, in some embodiments, the beamforming system includes a singlebeamformer with multiple beamformees, or multiple beamformers with morethan one beamformee. In another example, although the beamforming systemis shown in FIG. 1 as being connected in a certain topology, the networktopology of the beamforming system is not limited to the topology shownin FIG. 1.

In the embodiment depicted in FIG. 1, the beamformer 104 includes twoantennas, implemented as beamformer antennas 106-1 and 106-2. In such anembodiment, the beamformer antennas may be beamformer antenna-1 106-1and beamformer antenna-2 106-2. In an embodiment, the beamformerantennas 106-1 and 106-2 may be transmit antennas, such that transmitantennas may transmit information to other devices. In anotherembodiment, the beamformer antennas 106-1 and 106-2 may be receiveantennas, such that receive antennas may receive information from otherdevices. The beamformer antennas 106-1 and 106-2 may be implemented inhardware (e.g., circuits), software, firmware, or a combination thereof.The beamformer antennas 106-1 and 106-2 may be fully or partiallyimplemented as part of an integrated circuit (IC) device. In someembodiments, the beamformer antennas 106-1 and 106-2 are implemented aspart of wireless APs compatible with at least one WLAN communicationsprotocol (e.g., at least one IEEE 802.11 protocol). For example, thebeamformer antennas 106-1 and 106-2 may be part of wireless APscompatible with the IEEE 802.11be protocol.

In some embodiments, a beamformer (e.g., beamformer 104) connects to alocal area network (e.g., a LAN) and/or to a backbone network (e.g., theInternet) through a wired connection and wirelessly connects tobeamformees (e.g., wireless STAs), for example, through one or more WLANcommunications protocols, such as the IEEE 802.11 protocol. In someembodiments, a beamformer (e.g., beamformer 104) includes at least oneAP with at least one antenna (e.g., beamformer antenna-1 106-1 and/orbeamformer antenna-2 106-2), at least one transceiver operably connectedto the at least one antenna, and at least one controller operablyconnected to the corresponding transceiver. In some embodiments, the atleast one transceiver includes a physical layer (PHY) device. The atleast one controller may be configured to control the at least onetransceiver to process received packets through the at least oneantenna. In some embodiments, the at least one controller may beimplemented within a processor, such as a microcontroller, a hostprocessor, a host, a digital signal processor (DSP), or a centralprocessing unit (CPU), which can be integrated in a correspondingtransceiver. Although the beamformer 104 is shown in FIG. 1 as includingtwo beamformer antennas, other embodiments of the beamformer 104 mayinclude more than two beamformer antennas.

In the embodiment depicted in FIG. 1, the beamformee device, implementedas beamformee 108, includes two antennas which are implemented asbeamformee antennas 110-1 and 110-2. In such an embodiment, thebeamformee antennas may be beamformee antenna-1 110-1 and beamformeeantenna-2 110-2. In an embodiment, the beamformee antennas 110-1 and110-2 may be transmit antennas, such that transmit antennas may transmitinformation to other devices. In another embodiment, the beamformeeantennas 110-1 and 110-2 may be receive antennas, such that receiveantennas may receive information from other devices. The beamformeeantennas 110-1 and 110-2 may be implemented in hardware (e.g.,circuits), software, firmware, or a combination thereof. The beamformeeantennas 110-1 and 110-2 may be fully or partially implemented as partof an IC device. In some embodiments, the beamformee 108 may beimplemented as part of a wireless STA device that wirelessly connects towireless APs. For example, the beamformee 108 may be implemented in alaptop, a desktop personal computer (PC), a mobile phone, or othercommunications device that supports at least one WLAN communicationsprotocol. In some embodiments, the beamformee 108 may be acommunications device compatible with at least one IEEE 802.11 protocol(e.g., the IEEE 802.11be protocol).

In some embodiments, the beamformee antennas 110-1 and 110-2 may be partof wireless STAs compatible with the IEEE 802.11be protocol. In someembodiments, a wireless STA may include at least one antenna (e.g.,beamformee antenna-1 110-1 and/or beamformee antenna-2 110-2), at leastone transceiver operably connected to the at least one antenna, and atleast one controller connected to the corresponding transceiver. In someembodiments, the at least one transceiver includes a PHY device. The atleast one controller may be configured to control the at least onetransceiver to process received packets through the at least oneantenna. In some embodiments, the at least one controller may beimplemented within a processor, such as a microcontroller, a hostprocessor, a host, a DSP, or a CPU, which can be integrated in acorresponding transceiver. Although the beamformee 108 is shown in FIG.1 as including two beamformee antennas, other embodiments of thebeamformee 108 may include one beamformee antenna or more than twobeamformee antennas.

In the embodiment depicted in FIG. 1, the beamformee 108 communicateswith the beamformer 104 via two communication links, e.g., linkl 102-1and 1ink2 102-2. For example, each of the beamformee antennas 110-1 or110-2 communicates with beamformer antennas 106-1 or 106-2 viacorresponding communication links 102-1 or 102-2. In an embodiment,there may be four transmission paths (not shown), such that the fourtransmission paths may include transmissions from beamformer antenna-1106-1 to beamformee antenna-1 110-1, transmissions from beamformerantenna-1 106-1 to beamformee antenna-2 110-2, transmissions frombeamformer antenna-2 106-2 to beamformee antenna-2 110-2, and/ortransmissions from beamformer antenna-2 106-2 to beamformee antenna-1110-1. In such an embodiment, the four transmission paths may make upone communication link (not shown). In an embodiment, a communicationlink (e.g., link1 102-1 or link2 102-2) may include a Basic Service Set(BSS) operating channel established by a beamformer (e.g., beamformer104) that features multiple 20 MHz channels used to transmit packets(e.g., sounding packets, feedback packets, etc.) between a firstwireless device (e.g., beamformer 104) and a second wireless device(e.g., beamformee 108). As an example, a 20 MHz channel may include anumber of spatial streams (Nss) on which packets may be transmittedand/or received. In some embodiments, a 20 MHz channel may be apunctured 20 MHz channel or an unpunctured 20 MHz channel. In addition,although the beamformer 104 communicates (e.g., wirelessly communicates)with the beamformee 108 via multiple links 102-1 and 102-2, in otherembodiments, the beamformer 104 may communicate (e.g., wirelesslycommunicate) with the beamformee 108 via one link or more than twocommunication links.

In some embodiments, beamforming systems (e.g., beamforming system 100)may support devices (e.g., a beamformer device and/or a beamformeedevice) with up to 16 antennas for throughput and/or range enhancement.To support beamforming between such devices in beamforming systems, thedevices may use an implicit beamforming technique or an explicitbeamforming technique. As an example, implicit beamforming may involve abeamformer deriving a steering matrix from packets transmitted by thebeamformee, and explicit beamforming may involve a beamformee deriving asteering matrix to be used by the beamformer. However, in suchembodiments, beamforming may be difficult for devices with up to 16antennas as implicit beamforming may suffer from calibration issues atthe device(s) and explicit beamforming may need feedback on a channelvia a data payload in a feedback packet. Consequently, due to a largefeedback packet size, increased spatial dimensions supported bynon-legacy communication protocols (e.g., the IEEE 802.11be protocol)may cause significant feedback overhead when providing feedback on achannel. Thus, reducing overhead and/or calibration issues inbeamforming systems may help improve beamforming techniques for devicescommunicating in a beamforming system.

In accordance with an embodiment of the invention, a technique forbeamforming involves transmitting, by a beamformer to a beamformee, asounding packet that includes training symbols, receiving, at thebeamformee, the sounding packet that includes the training symbols,deriving, at the beamformee, channel estimates from the training symbolsincluded in the sounding packet, computing, at the beamformee, afeedback matrix from the derived channel estimates, transmitting, by thebeamformee to the beamformer, a packet that includes two sets ofsymbols, wherein the feedback matrix is applied to at least one of thetwo sets of symbols, receiving, at the beamformer, the packet thatincludes the two sets of symbols, and operating the beamformer accordingto the two sets of symbols included in the packet. In some embodiments,the feedback matrix includes right singular vectors derived from thechannel estimates, such that the beamformer may direct beam steering tothe beamformee using the right singular vectors derived from the channelestimates. By exchanging packets with symbols between the beamformer andthe beamformee to direct beam steering in beamforming systems, thebeamforming system may reduce overhead and/or calibration issues. Thus,reducing overhead and/or calibration issues in beamforming systems mayhelp further enhance beamforming techniques for devices communicating ina beamforming system by improving device efficiency and/or performance.

An example of a beamformer and a beamformee exchanging packets in abeamforming system is described in further detail with reference to FIG.2.

FIG. 2 illustrates an example of a beamformer and a beamformeeexchanging packets in accordance with an embodiment of the invention. Inparticular, FIG. 2 is shown as including a beamformer and a beamformee,implemented as beamformer 204 and beamformee 208, respectively. In anembodiment, the beamformer 204 and the beamformee 208 may be part of abeamforming system (e.g., beamforming system 100), such that thebeamformer 204 and the beamformee 208 communicate via a link,implemented as link 202. With reference to FIG. 2, the beamformer 204and the beamformee 208 may exchange packets via link 202 to direct beamsteering in the beamforming system. In some embodiments, the beamformer204 may transmit a Null Data Packet (NDP) Announcement packet 210 onlink 202 to the beamformee 208. In such an embodiment, after a firstShort Interframe Space (SIFS) time 200-1, the beamformer 204 maytransmit an NDP packet 212 on link 202 to the beamformee 208. As anexample, the NDP packet 212 may be a sounding packet that includestraining symbols (e.g., Long Training Field (LTF) symbols). In such anembodiment, after a second SIFS time 200-2, the beamformer 204 maytransmit a trigger packet 214 on link 202 to the beamformee 208, suchthat the trigger packet 214 may solicit a response from the beamformee208.

In such an embodiment, once the beamformee 208 has received the NDPAnnouncement packet 210, the NDP packet 212, and the trigger packet 214,the beamformee may transmit, after a third SIFS time 200-3, a feedbackpacket 216 on link 202 to the beamformer 204 in response to the receivedpackets from the beamformer 204. As an example, the feedback packet 216may be a packet that includes two sets of symbols. In such an example, afeedback matrix derived from channel estimates (at the beamformee 208)may be applied to at least one of the two sets of symbols, such thatapplying the feedback matrix to at least one of the two sets of symbolsmay involve, e.g., multiplying a Hermitian transpose of the feedbackmatrix with a (second) training sequence to form a second set ofsymbols. In an embodiment, applying the feedback matrix to at least oneof the two sets of symbols may also involve other similar steps. In anembodiment, the feedback matrix may include right singular vectorsderived from the channel estimates. Furthermore, after the beamformer204 receives the feedback packet 216 on link 202 from the beamformee208, the beamformer may transmit a steered packet 218 on link 202 to thebeamformee 208. As an example, the steered packet 218 may be transmittedvia directed beam steering by the beamformer 204 to the beamformee 208,such that beam steering may be performed using right singular vectorsderived from channel estimates at the beamformer 204.

Examples of packets that may be exchanged in a beamforming system aredescribed in further detail with reference to FIG. 3 and FIGS. 4A-4B.

FIG. 3 depicts an example of a packet, 300, in accordance with anembodiment of the invention. As an example, the packet 300 may be asounding packet (e.g., NDP packet) that includes training symbols (e.g.,LTF symbols). In some embodiments, the packet 300 may be transmitted bya beamformer (e.g., beamformer 104) to a beamformee (e.g., beamformee108) in a beamforming system (e.g., beamforming system 100) to helpdirect beam steering. In an embodiment, the packet 300 may have an EHTpacket format, such that the packet 300 may be in accordance with theEHT communication protocol.

With reference to FIG. 3, the packet 300 is shown as including at leastnine fields, implemented as a first field, Legacy Short Training Field(L-STF) field 302 that is 8 μs, a second field, Legacy Long TrainingField (L-LTF) field 304 that is 8 μs, a third field, Legacy Signal(L-SIG) field 306 that is 4 μs, a fourth field, Repeated L-SIG (RL-SIG)field 308 that is 4 μs, a fifth field, Universal Signal (U-SIG) field310 that is 8 μs, a sixth field, EHT Signal (EHT-SIG) field 312 that is4 μs, a seventh field, EHT Short Training Field (EHT-STF) field 314 thatis 4 μs, an eighth field, first EHT LTF (EHT-LTF1) field 316-1 that is16 μs, additional EHT-LTF (EHT-LTFN) field(s) 316-N that may be 16 μsand where N may be an integer greater than one, and a ninth field,Packet Extension (PE) field 318 that may be, e.g., 8 μs. In anembodiment, the training symbols (e.g., LTF symbols) may be implementedvia EHT-LTF fields (e.g., EHT-LTF1 field 316-1 and/or EHT-LTFN field(s)316-N). In such an embodiment, there may be at least as many trainingsymbols as a number of antennas at the beamformer (NTX). For example, ifthe beamformer has 16 antennas, then the sounding packet (e.g., packet300) may include 16 training symbols implemented via EHT-LTF fields froman EHT-LTF1 field to an EHT-LTF16 field.

FIG. 4A depicts another example of a packet, 400-1, in accordance withan embodiment of the invention. As an example, the packet 400-1 may be afeedback packet (e.g., feedback packet 216) that includes two sets ofsymbols (e.g., training symbols, LTF symbols, etc.). In such an example,the two sets of symbols included in the packet 400-1 may not berepeated. In some embodiments, the packet 400-1 may be transmitted by abeamformee (e.g., beamformee 108) to a beamformer (e.g., beamformer 104)in a beamforming system (e.g., beamforming system 100) to help directbeam steering. In an embodiment, the packet 400-1 may have an EHT packetformat, such that the packet 400-1 may be in accordance with the EHTcommunication protocol.

With reference to FIG. 4A, the packet 400-1 is shown as including atleast ten fields, implemented as a first field, L-STF field 402 that is8 μs, a second field, L-LTF field 404 that is 8 μs, a third field, L-SIGfield 406 that is 4 μs, a fourth field, RL-SIG field 408 that is 4 μs, afifth field, U-SIG field 410 that is 8 μs, a sixth field, EHT-STF field412 that is 8 μs, a first set of symbols, set 1 414 a, that includes aseventh field, EHT-LTF1 field 414-1 a that is 4 μs, and an eighth field,EHT-LTF2 field 414-2 a that is 4 μs, a second set of symbols, set 2 414b, that includes a ninth field, EHT-LTF1 414-1 b that is 4 μs, andadditional EHT-LTF field(s), EHT-LTFN 414-Nb that may be 4 μs and whereN may be an integer greater than one, and a tenth field, PE 416 that maybe, e.g., 8 μs.

With further reference to FIG. 4A, a feedback matrix may be computedfrom derived channel estimates by a beamformee (e.g., beamformee 108)and applied to at least one of the two sets of symbols (e.g., set 1 414a and/or set 2 414 b) included in the packet 400-1. In some embodiments,the first set of symbols (e.g., set 1 414 a) may include a sequence oftraining symbols and the second set of symbols (e.g., set 2 414 b) mayinclude the sequence of training symbols included in the first set ofsymbols with the applied feedback matrix. In an embodiment, columns ofthe applied feedback matrix may be an orthonormal spatial spreadingmatrix. In such an embodiment, the first set of symbols (e.g., set 1 414a) may include a sequence of training symbols and the second set ofsymbols (e.g., set 2 414 b) may include the sequence of training symbolsincluded in the first set of symbols with the applied orthonormalspatial spreading matrix. In some embodiments, the first set of symbols(e.g., set 1 414 a) may include a sequence of training symbols and thesecond set of symbols (e.g., set 2 414 b) may include a differentsequence of training symbols, such that the sequence of training symbolsin each set of symbols may have different dimensions. In someembodiments, the beamformee may apply another orthonormal matrix to thefirst set of symbols and may apply the feedback matrix in addition tothe orthonormal matrix to the second set of symbols.

With further reference to FIG. 4A, in such embodiments, the first set ofsymbols (e.g., set 1 414 a) may include at least as many trainingsymbols as N_(SS) and the second set of symbols (e.g., set 2 414 b) mayinclude at least as many training symbols as N_(Tx). For example, if thebeamformee has an N_(SS) of two and the beamformer has an N_(Tx) of 16,then the first set of symbols (e.g., set 1 414 a) may have at least twosymbols (e.g., two LTF symbols) and the second set of symbols (e.g., set2 414 b) may have at least 16 symbols (e.g., 16 LTF symbols).

FIG. 4B depicts another example of a packet, 400-2, in accordance withan embodiment of the invention. As an example, the packet 400-2 may be afeedback packet (e.g., feedback packet 216) that includes two sets ofsymbols (e.g., training symbols, LTF symbols, etc.). In such an example,a first set of symbols may be repeated N times and a second set ofsymbols may be repeated M times, such that N and M may be integersgreater than one. In some embodiments, the packet 400-2 may betransmitted by a beamformee (e.g., beamformee 108) to a beamformer(e.g., beamformer 104) in a beamforming system (e.g., beamforming system100) to help direct beam steering. In an embodiment, the packet 400-2may have an EHT packet format, such that the packet 400-2 may be inaccordance with the EHT communication protocol.

With reference to FIG. 4B, the packet 400-2 is shown as including atleast thirteen fields, implemented as a first field, L-STF field 402that is 8 μs, a second field, L-LTF field 404 that is 8 μs, a thirdfield, L-SIG field 406 that is 4 μs, a fourth field, RL-SIG field 408that is 4 μs, a fifth field, U-SIG field 410 that is 8 μs, and a sixthfield, EHT-STF field 412 that is 8 μs. In an embodiment, the packet400-2 includes a first repetition set, repetition set 1 414-1, thatincludes a first set of symbols, set 1 414 a, that includes a seventhfield, EHT-LTF1 field 414-1 a that is 4 μs, and an eighth field,EHT-LTF2 field 414-2 a that is 4 μs, and a repeated first set ofsymbols, set 1-N 414 a-N that includes a ninth field, EHT-LTF1 field414-1 a that is 4 μs, and a tenth field, EHT-LTF2 field 414-2 a that is4 μs. In an embodiment, the packet includes a second repetition set,repetition set 2 414-2, that includes a second set of symbols, set 2 414b, that includes an eleventh field, EHT-LTF1 414-1 b that is 4 μs, andadditional EHT-LTF field(s), EHT-LTFN 414-Nb that may be 4 μs and whereN may be an integer greater than one, and a repeated second set ofsymbols, set 2-M 414 b-M, that includes a twelfth field, EHT-LTF1 414-1b that is 4 μs, and additional EHT-LTF field(s), EHT-LTFN 414-Nb thatmay be 4 μs and where N may be an integer greater than one.

In such an embodiment, the packet 400-2 also includes a thirteenthfield, PE 416 that may be, e.g., 8 μs. As an example, N of set 1-N 414a-N may be a different integer from N of EHT-LTFN 414-Nb in set 2 414 band N of EHT-LTFN 414-Nb in set 2-M 414 b-M.

With further reference to FIG. 4B, the fields included in set 1-N 414a-N and set 2-M 414 b-M may each be repetitions (e.g., be similar to,contain the same contents, be the same as, etc.) of the fields includedin set 1 414 a and set 2 414 b, respectively. In some embodiments, afeedback matrix may be computed from derived channel estimates by abeamformee (e.g., beamformee 108) and applied to at least one of the twosets of symbols (e.g., set 1 414 a (and set 1-N 414 a-N) and/or set 2414 b (and set 2-M 414 b-M)) included in the packet 400-2. In someembodiments, the first set of symbols (e.g., set 1 414 a (and set 1-N414 a-N)) may include a sequence of training symbols and the second setof symbols (e.g., set 2 414 b (and set 2-M 414 b-M)) may include thesequence of training symbols included in the first set of symbols withthe applied feedback matrix. In an embodiment, columns of the appliedfeedback matrix may be an orthonormal spatial spreading matrix. In suchan embodiment, the first set of symbols (e.g., set 1 414 a (and set 1-N414 a-N)) may include a sequence of training symbols and the second setof symbols (e.g., set 2 414 b (and set 2-M 414 b-M)) may include thesequence of training symbols included in the first set of symbols withthe applied orthonormal spatial spreading matrix. In some embodiments,the beamformee may apply another orthonormal matrix to the first set ofsymbols (e.g., set 1 414 a (and set 1-N 414 a-N)) and may apply thefeedback matrix in addition to the orthonormal matrix to the second setof symbols (e.g., set 2 414 b (and set 2-M 414 b-M)). In such anembodiment, the orthonormal matrix may be a steering matrix that may becomputed implicitly with respect to an up-link (UL) channel. In someembodiments, the first set of symbols (e.g., set 1 414 a (and set 1-N414 a-N)) may include a sequence of training symbols and the second setof symbols (e.g., set 2 414 b (and set 2-M 414 b-M)) may include adifferent sequence of training symbols, such that the sequence oftraining symbols in each set of symbols may have different dimensions.

With further reference to FIG. 4B, in such embodiments, the first set ofsymbols (e.g., set 1 414 a (and set 1-N 414 a-N)) may include at leastas many training symbols as Nss and the second set of symbols (e.g., set2 414 b (and set 2-M 414 b-M)) may include at least as many trainingsymbols as NTX. For example, if the beamformee has an N_(SS) of two andthe beamformer has an NTX of 16, then the first set of symbols (e.g.,set 1 414 a (and set 1-N 414 a-N)) may have at least two symbols (e.g.,two LTF symbols) and the second set of symbols (e.g., set 2 414 b (andset 2-M 414 b-M)) may have at least 16 symbols (e.g., 16 LTF symbols).

A functional block diagram that depicts operations at a beamformer and abeamformee while exchanging packets to direct beam steering is describedin further detail with reference to FIG. 5.

FIG. 5 depicts a functional block diagram, 500, of operations at abeamformer and a beamformee while exchanging packets in accordance withan embodiment of the invention. At block 502, a beamformer (e.g.,beamformer 104) may transmit training symbols (e.g., LTF symbols) to abeamformee (e.g., beamformee 108) for channel estimation via a soundingpacket (e.g., packet 300). In an embodiment, the beamformee may receivethe sounding packet that includes the training symbols, and at block504, the beamformee may perform channel estimation. As an example,performing channel estimation at the beamformee may involve derivingchannel estimates (H_(DL)) from the training symbols included in thepacket to compute a feedback matrix (V). In such an example, V may be amatrix formed by right singular vectors of, e.g., H_(DL), with adimension of N_(Tx)×N_(Tx). In an embodiment, H_(DL) may represent adown-link (DL) channel coefficient matrix from beamformer to beamformeewith a dimension of N_(Rx)×N_(Tx), such that N_(Rx) represents a numberof antennas at a beamformee. At block 506, the beamformee may compute V(e.g., a steering matrix) from H_(DL). As an example, V may includeright singular vectors derived from H_(DL). At block 508, the beamformeemay transmit feedback to the beamformer via a packet (e.g., packet 400-1or packet 400-2) that includes two sets of symbols. As an example, thepacket that includes two sets of symbols may use N_(ss) or more trainingsymbols without applying V for a first set of symbols and may use N_(Tx)or more symbols and apply V for a second set of symbols.

In an embodiment, the beamformer may receive the packet that includesthe two sets of symbols from the beamformee, and at block 510, thebeamformer may perform channel estimation. As an example, performingchannel estimation at the beamformer may involve computing two sets ofchannel coefficients from the packet that includes the two sets ofsymbols. In an embodiment, a first set of channel coefficients may bederived from the first set of symbols and may be represented by H_(UL),such that H_(UL) represents a UL channel coefficient matrix from thebeamformee to the beamformer with a dimension of N_(Tx)×N_(Rx).Additionally, in such an embodiment, a second set of channelcoefficients may be derived from the second set of symbols and may berepresented by H_(UL)V^(H), such that V^(H) represents a conjugatetranspose (e.g., Hermitian transpose) of V.

At block 512, the beamformer may recover V by extracting V from the twosets of channel coefficients. As an example, the beamformer may recoverV using the two sets of channel coefficients by removing H_(UL). In suchan example, recovering V using the two set of channel coefficients mayinvolve computing a first orthonormal matrix (Q₁) by deriving a firstHermitian transpose ((H_(UL))^(H)) of the first channel coefficientmatrix (H_(UL)) from at least one of the two sets of channelcoefficients, then deriving a first QR decomposition (Q) of the firstHermitian transpose ((H_(UL))^(H)) to determine the first orthonormalmatrix (Q₁=Q). In addition, in such an example, recovering V using thetwo sets of channel coefficients may involve computing a secondorthonormal matrix (Q₂) by deriving a second Hermitian transpose(V(H_(UL))^(H)) of the second channel coefficient matrix (H_(UL)V^(H))from at least one of the two sets of channel coefficients, then derivinga second QR decomposition (VQ) of the second Hermitian transpose(V(H_(UL))^(H)) to determine the second orthonormal matrix (Q₂=VQ).Furthermore, in such an example, a third matrix with orthogonal columnsmay be derived from the first orthonormal matrix (Q₁=Q) and the secondorthonormal matrix (Q₂=VQ), such that the third matrix may be thefeedback matrix (V=Q₂(Q₁)^(H)). In an embodiment, the feedback matrix(V=Q₂(Q₁)^(H)) may be an estimated feedback matrix. At block 514, thebeamformer may transmit a steered packet (e.g., steered packet 218) tothe beamformee using the feedback matrix (V=Q₂(Q₁)^(H)), such that thefeedback matrix (V=Q₂(Q₁)^(H)) helps direct beam steering to thebeamformee.

With reference to FIG. 5, in an alternative embodiment, at block 508,the beamformee may apply another orthonormal matrix (e.g., Q) to thefirst set of symbols and may apply the feedback matrix in addition tothe orthonormal matrix (e.g., QV^(H)) to the second set of symbols. Insome embodiments, at block 508, the beamformee may transmit at least onedata symbol that includes additional beamforming information (e.g.,sub-stream signal-to-noise ratio (SNR)). In an alternative embodiment,at block 512, the beamformer may select corresponding columns from thesecond orthonormal matrix (Q₂) and may post-multiply a sub-matrix (e.g.,P₂) formed by the corresponding columns from the second orthonormalmatrix (Q₂) with the first Hermitian transpose (Q₁ ^(H)) of the firstorthonormal matrix (Q₁) to derive the third matrix (P₂Q₁ ^(H)) withorthogonal columns.

An example of operations between a beamformer and a beamformee whileexchanging packets to direct beam steering is described in furtherdetail with reference to FIG. 6.

FIG. 6 illustrates an example of operations between a beamformer and abeamformee while exchanging packets to direct beam steering inaccordance with an embodiment of the invention. In particular, theoperations between a beamformer 604 that includes four beamformerantennas (e.g., beamformer antenna-1 606-1, beamformer antenna-2 606-2,beamformer antenna-3 606-3, and beamformer antenna-4 606-4) and abeamformee 608 that includes two antennas (e.g., beamformee antenna-1610-1 and beamformee antenna-2 610-2) may involve three steps,implemented as step 1 600-1, step 2 a 600-2 a, step 2 b 600-2 b, step 3a 600-3 a, and step 3 b 600-3 b. In such an embodiment, the beamformer604 and the beamformee 608 may communicate via eight transmission paths(not shown).

In an embodiment, step 1 600-1 may involve implementing block 502 of thefunctional block diagram 500, such that the beamformer 604 transmits asounding packet (e.g., packet 300) that includes symbols, e.g., trainingsymbols (shown by X_(train) (known)), to the beamformee 608 via a firstbeam direction 602-1. In an embodiment, step 2 a 600-2 a may involveimplementing block 504 of the functional block diagram 500, such thatthe beamformee 608 performs channel estimation by deriving channelestimates (e.g., H_(DL)) (shown by H) from the DL transmission oftraining symbols (shown by HX_(train)) from the beamformer 604. In suchan embodiment, step 2 a 600-2 a may also involve implementing block 506of the functional block diagram 500, such that the beamformee 608 maycompute a feedback matrix (shown by V) by, for example, taking asingular value decomposition of the derived DL channel estimates (e.g.,H).

In an embodiment, step 2 b 600-2 b may involve implementing block 508 ofthe functional block diagram 500, such that the beamformee 608 maytransmit a packet (e.g., packet 400-1 or packet 400-2) that includes twosets of symbols to the beamformer 604 via a second beam direction 602-2.In such an embodiment, the two sets of symbols may include a first setof symbols that may include a sequence of training symbols (shown byX_(train) ¹) and a second set of symbols that may include the sequenceof training symbols included in the first set of symbols with thefeedback matrix (shown by V^(H)X_(train) ²). In some embodiments, thefirst set of symbols may include a sequence of training symbols and thesecond set of symbols may include a different sequence of trainingsymbols, such that the sequence of training symbols in each set ofsymbols may have different dimensions.

In an embodiment, step 3 a 600-3 a may involve implementing block 510 ofthe functional block diagram 500, such that the beamformer 604 mayreceive the UL packet that includes the two sets of symbols from thebeamformee 608 and may perform channel estimation by computing two setsof channel coefficients from UL channel estimates (e.g., H_(UL)) derivedfrom the two sets of symbols included in the packet. For example, afirst set of UL channel estimates (shown by GX_(train) ¹) may be derivedfrom the first set of symbols (X_(train) ¹) and a second set of ULchannel estimates (shown by GV^(H)X_(train) ²) may be derived from thesecond set of symbols (V^(H)X_(train) ²). In such an example, thebeamformer 604 may compute a first set of channel coefficients (shown byG^(H)) and a second set of channel coefficients (shown by VG^(H)) fromthe first set of UL channel estimates (shown by GX_(train) ¹) and thesecond set of UL channel estimates (shown by GV^(H)X_(train) ²),respectively.

In an embodiment, step 3 b 600-3 b may involve implementing block 512 ofthe functional block diagram 500, such that the beamformer 604 mayextract a feedback matrix (shown by V) from the two sets of channelcoefficients. In an embodiment, the feedback matrix may be a matrixformed by right singular vectors of, e.g., H_(DL), with a dimension ofN_(Tx)×N_(SS). As an example, the feedback matrix may be a sub-matrix ofthe matrix formed by the right singular vectors of H_(DL). In such anembodiment, the beamformer 604 may direct beam steering to thebeamformee 608 in subsequent steered packet transmissions (not shown)using the right singular vectors derived from the channel estimates,such that the subsequent transmissions may involve implementing block514 of the functional block diagram 500.

FIG. 7 illustrates a flow diagram of a technique for beamforming inaccordance with an embodiment of the invention. At block 702, abeamformer may transmit to a beamformee, a sounding packet that includestraining symbols. At block 704, the beamformee may receive the soundingpacket that includes the training symbols. At block 706, the beamformeemay derive channel estimates from the training symbols included in thesounding packet. At block 708, the beamformee may compute a feedbackmatrix from the derived channel estimates. At block 710, the beamformeemay transmit to the beamformer, a packet that includes two sets ofsymbols, where the feedback matrix is applied to at least one of the twosets of symbols. At block 712, the beamformer may receive the packetthat includes the two sets of symbols. At block 714, the beamformer mayoperate according to the two sets of symbols included in the packet.

With reference to FIG. 5, FIG. 6, and/or FIG. 7, in some embodiments,the techniques performed by the beamformer (e.g., beamformer 104) and/orthe beamformee (e.g., beamformee 108) with respect to the steps and/orfunctional blocks for beam steering in a beamforming system (e.g.,beamforming system 100) may be implemented via a processor and/orcontroller included in a device (e.g., beamformer 104 and/or beamformee108). In some embodiments, the processor that performs the steps and/orfunctional blocks for beam steering in the beamforming system may beoperably connected to the controller included in the device(s). As anexample, the controller may perform functionalities previously describedwith reference to FIG. 5, FIG. 6, and/or FIG. 7.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be implemented in anintermittent and/or alternating manner.

It should also be noted that at least some of the operations for themethods described herein may be implemented using software instructionsstored on a computer useable storage medium for execution by a computer.As an example, an embodiment of a computer program product includes acomputer useable storage medium to store a computer readable program.

The computer-useable or computer-readable storage medium can be anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system (or apparatus or device). Examples ofnon-transitory computer-useable and computer-readable storage mediainclude a semiconductor or solid-state memory, magnetic tape, aremovable computer diskette, a random-access memory (RAM), a read-onlymemory (ROM), a rigid magnetic disk, and an optical disk. Currentexamples of optical disks include a compact disk with read only memory(CD-ROM), a compact disk with read/write (CD-R/W), and a digital videodisk (DVD).

Alternatively, embodiments of the invention may be implemented entirelyin hardware or in an implementation containing both hardware andsoftware elements. In embodiments which use software, the software mayinclude but is not limited to firmware, resident software, microcode,etc.

Although specific embodiments of the invention have been described andillustrated, the invention is not to be limited to the specific forms orarrangements of parts so described and illustrated. The scope of theinvention is to be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A method for beamforming, the method comprising:transmitting, by a beamformer to a beamformee, a sounding packet thatincludes training symbols; receiving, at the beamformee, the soundingpacket that includes the training symbols; deriving, at the beamformee,channel estimates from the training symbols included in the soundingpacket; computing, at the beamformee, a feedback matrix from the derivedchannel estimates; transmitting, by the beamformee to the beamformer, apacket that includes two sets of symbols, wherein the feedback matrix isapplied to at least one of the two sets of symbols; receiving, at thebeamformer, the packet that includes the two sets of symbols; andoperating the beamformer according to the two sets of symbols includedin the packet.
 2. The method of claim 1, wherein the sounding packetincludes at least as many training symbols as a number of antennas atthe beamformer (N_(Tx)).
 3. The method of claim 1, wherein the feedbackmatrix includes right singular vectors derived from the channelestimates.
 4. The method of claim 3, wherein the beamformer directs beamsteering to the beamformee using the right singular vectors derived fromthe channel estimates.
 5. The method of claim 1, wherein the packet thatincludes the two sets of symbols includes: a first set of symbols thatinclude a sequence of training symbols; and a second set of symbols thatinclude the sequence of training symbols included in the first set ofsymbols with the applied feedback matrix.
 6. The method of claim 5,wherein columns of the applied feedback matrix are an orthonormalspatial spreading matrix, and wherein the beamformee applies anotherorthonormal matrix to the first set of symbols and applies the feedbackmatrix in addition to the orthonormal matrix to the second set ofsymbols.
 7. The method of claim 6, wherein the first set of symbolsincludes at least as many training symbols as a number of spatialstreams (N_(SS)) and the second set of symbols includes at least as manytraining symbols as N_(Tx).
 8. The method of claim 1, wherein columns ofthe applied feedback matrix are an orthonormal spatial spreading matrix.9. The method of claim 8, wherein the packet that includes the two setsof symbols includes: a first set of symbols that include a sequence oftraining symbols; and a second set of symbols that include the sequenceof training symbols included in the first set of symbols with theapplied orthonormal spatial spreading matrix.
 10. The method of claim 9,wherein the beamformee applies another orthonormal matrix to the firstset of symbols and applies the feedback matrix in addition to theorthonormal matrix to the second set of symbols.
 11. The method of claim10, wherein the first set of symbols includes at least as many trainingsymbols as Nss and the second set of symbols includes at least as manytraining symbols as N_(Tx).
 12. The method of claim 1, wherein thebeamformer computes two sets of channel coefficients from the packetthat includes the two sets of symbols.
 13. The method of claim 12,wherein the beamformer recovers the feedback matrix using the two setsof channel coefficients.
 14. The method of claim 13, wherein recoveringthe feedback matrix using the two sets of channel coefficients includes:computing a first orthonormal matrix by: deriving a first Hermitiantranspose of a first channel coefficient matrix from at least one of thetwo sets of channel coefficients; deriving a first QR decomposition ofthe first Hermitian transpose to determine the first orthonormal matrix;computing a second orthonormal matrix by: deriving a second Hermitiantranspose of a second channel coefficient matrix from at least one ofthe two sets of channel coefficients; deriving a second QR decompositionof the second Hermitian transpose to determine the second orthonormalmatrix; and deriving a third matrix with orthogonal columns from thefirst orthonormal matrix and the second orthonormal matrix, wherein thethird matrix is the feedback matrix.
 15. The method of claim 14, whereinthe beamformer selects corresponding columns from the second orthonormalmatrix and post-multiplies a sub-matrix formed by the correspondingcolumns from the second orthonormal matrix with the first Hermitiantranspose of the first orthonormal matrix to derive the third matrixwith orthogonal columns.
 16. The method of claim 1, wherein the trainingsymbols included in the packet are Long Training Field (LTF) symbols.17. The method of claim 9, wherein the first set of symbols is repeatedN times and the second set of symbols is repeated M times, wherein N andM are integers greater than one.
 18. The method of claim 1, wherein thebeamformee transmits at least one data symbol that includes at least onesub-stream signal-to-noise ratio (SNR).
 19. A beamforming system, thebeamforming system comprising: a beamformer including a processorconfigured to: transmit a sounding packet that includes trainingsymbols; receive a packet that includes two sets of symbols; operateaccording to the two sets of symbols included in the packet; abeamformee including a processor configured to: receive the soundingpacket that includes the training symbols; derive channel estimates fromthe training symbols included in the sounding packet; compute a feedbackmatrix from the derived channel estimates; and transmit the packet thatincludes the two sets of symbols, wherein the feedback matrix is appliedto at least one of the two sets of symbols.
 20. A device, the devicecomprising: a processor configured to: operate as a beamformer, whereinoperating as a beamformer involves: transmitting a sounding packet thatincludes training symbols; receiving a packet that includes two sets ofsymbols; operating according to the two sets of symbols included in thepacket; and operate as a beamformee, wherein operating as a beamformeeinvolves: receiving the sounding packet that includes the trainingsymbols; deriving channel estimates from the training symbols includedin the sounding packet; computing a feedback matrix from the derivedchannel estimates; and transmitting the packet that includes the twosets of symbols, wherein the feedback matrix is applied to at least oneof the two sets of symbols.